Pulsewidth coding approach for multi-sensor synchronization of urban mobile mapping system

Mobile mapping system has become an irresistible trend used for 3D urban environment modeling, transportation engineering, road survey and other applications during last few years. A typical car-borne laser scanner based mobile mapping system today can be considered as a multi-sensor system that integrates various navigation devices and data acquisition sensors on a rigid, moving platform like a van or any other vehicle for determining the positions of the surrounding objects along the driving trajectory. All these sensors in the mobile mapping system are synchronized to the GPS time via geo-referencing system. With traditional synchronizing method, the hardware restriction of the geo-referencing system limits the number (kind) of sensors to be synchronized. The paper presents a synchronization approach which applies pulsewidth coding into synchronizing pulse generation. The approach enables geo-referencing system to be synchronized with more sensors and breaks the limitation of hardware. The accuracy of the approach is analyzed after a test bench is presented. The advantages and disadvantages of the approach are discussed correspondingly.